Light diffusing tip

ABSTRACT

A light diffusing tip is provided. The light diffusing tip comprises a housing and a monolithic light scattering medium disposed within the housing. The monolithic light scattering medium comprises a first scattering region at a first position, the scattering region having a first scattering property and a second scattering region at a second position, the second scattering region having a second scattering property different from the first scattering property, wherein the first scattering region and the second scattering region are coextensive along a substantial portion of a length of the housing. A light diffusing applicator also is provided. The light diffusing applicator comprises at least one optical waveguide, a first termination coupled to a first end of the at least one optical waveguide, the first termination to couple to a light source and a light diffusing tip coupled to a second end of the at least one optical waveguide.

CROSS-REFERENCE TO RELATED APPLICATION(S)

The present application is a divisional application of and claimspriority from U.S. patent application Ser. No. 10/989,894, filed Nov.16, 2004, entitled “LIGHT DIFFUSING TIP,” naming inventors Ashok Gowda,Roger McNichols, Marc Gelnett, and Mathew Fox, which application isincorporated by reference herein in its entirety.

FIELD OF THE DISCLOSURE

The present disclosure relates generally to fiber optic lightapplicators and more particularly to light diffusion devices.

BACKGROUND

Light diff-using tip applicators find application in a number ofclinical settings. Prevalent uses include the treatment of canceroustumors using either photodynamic therapy (PDT) or laser interstitialthermal therapy (LITT). In PDT, light diff-using fiber optics are usedto uniformly irradiate an organ or tissue that has been previouslytreated with a photo-sensitive light-activated compound which has beenallowed to accumulate in the tumor. In LITT, laser energy is applied totissues for treating solid malignant tumors in various organs such asthe liver, brain, ear nose or throat (ENT), or abdominal tissues, aswell as for treating benign alterations such as prostate adenomas,Volumetric heating within target tissues during LITT results in thermaltissue necrosis and tumor death.

Light diffusing tip applicators used to carry light from a source into atarget tissue during such therapies can vary significantly in terms oftheir size and shape, as well as the way that they distribute light. Aconventional bare fiber optic that terminates in a cleaved or polishedface perpendicular to the optic axis is limited in most PDT and LITTprocedures. To illustrate, for, LITT procedures the power density andresulting heat generation using a bare fiber often exceed the thermaldiffusion into the tissue, and areas close to the applicator thereforechar or vaporize. These tissue phenomena are problematic for creatingcontrolled photothermal lesions For example, charring limits heatdeposition within deeper tissue volumes due to increased absorption oflight energy by the charred region. As charred tissue continues toabsorb incident light, its temperature continues to rise leading to morecarbonization around the applicator, and temperature rise in deeperlayers is strictly dependent on heat conduction away from thiscarbonized volume. While it is possible to create large thermal lesionsin this manner, the morphology of the resulting lesion is highlyundesirable. Furthermore, the high temperatures associated with thecarbonized tissue often result in burning and failure at the tip of theoptical fiber with significant attendant risk for patients andequipment. Therefore, many LITT procedures employ an applicator with alight diffuser (or diffusing tip) at the delivery end of the opticalfiber. In such applications, the scattering of light over a largersurface area provided by the diffusing tip reduces the power density onthe adjacent tissue and creates a larger coagulation volume whileminimizing char formation,

Several techniques have been developed to obtain scattering of lightfrom an optical fiber. One conventional technique includes selecting theratio of the index of refraction between the core of the optical fiberand the transparent cladding such that total internal reflection isprevented, thereby allowing light to escape and radiate outside of thefiber. It is difficult, however, to achieve uniform output intensityusing this method, and its use therefore is not widespread. Otherconventional techniques include etching the outer surface of the core orclad using chemical or mechanical means or embedding scatteringparticles around the outer surface of the core or within the cladding.Such techniques typically result in a decrease in the mechanicalintegrity of the fiber and frequently are incapable of achieving a widerange of light distributions.

Another conventional technique employs the use of a transmissive mediumsuch as an epoxy with embedded scattering particles and a reflector atthe tip. The reflector serves to both improve homogeneity of the lightexiting the fiber as well as prevent significant forward lightpropagation. However, the use of metallic or dielectric reflectors orplugs limits the utility of such sensors because such reflectors mayabsorb light energy and lead to fiber failure. Moreover; metalreflectors, in particular, may not be compatible with new magneticresonance imaging (MRI) image-guided procedures. A further disadvantageis that such reflectors may be difficult or expensive to produce.Finally, the reflector and scattering medium, being of significantlydifferent materials with differing mechanical properties, may partiallyor fully separate at their interface, leading to potential “hot spots,”undesirable light distributions, or degradation of diffuser performance,all of which are likely to lead to a failure in the applicator

Another conventional technique employs a cylindrical diffusing tip thatincludes an optically transparent core material such as silicone withscattering particles dispersed therein which abuts the core of theoptical fiber. This diffusing tip is manufactured such that theconcentration of scattering particles continuously increases from theproximal to distal ends of the diffusing tip. The increase in theconcentration of scattering particles eliminates the need for areflector because light is increasingly scattered along the diffusingtip length while the amount of light available decreases distally.However, this conventional technique has a number of limitations. Forone, the gradient in the tip is extruded using a two-channel injectorsystem with a mixing chamber whose contents are combined and extrudedthrough a die. The contents are combined by varying the relative feedrates of elastomer with two different concentrations of scatterers tocreate a gradient in the scattering particles along the axial length ofthe diffusing tip,. This mixing process places fundamental limitationson the range of gradients (e.g., the rate of change of said gradients)which can be produced. Moreover, this mixing process allows for thecreation of gradients only in the direction of the axis of the fiber. Aradial gradient in scattering particle concentration, for example, isunachievable by this conventional process.

Further, the elastomer-based tip is first extruded as described above,cut to length and then affixed to the end of the terminus face of thedelivery fiber. A plastic tube then is slid over both the jacket of theoptical fiber and the diffuser core. Thus the diffuser core must beseparately affixed to the optical fiber core which results in a smallbonding surface area. Further, an outer tube larger than the fiber'souter jacket is required, thereby increasing the overall diameter of thedevice beyond the outer diameter of the fiber's outer jacket. Anotherdisadvantage related to affixing the tip in this manner is that thereare no bonding interfaces to any circumferential surfaces of the fiber.The sole axial bond is vulnerable to defects such as air gaps,especially when flexion occurs at the interface between the opticalfiber core and diffuser core that causes the two to separate Air orother gaps between the optical fiber core and diffuser core change theintended light distribution and may result in unintended “hot spots”which significantly increase the risk of fiber failure during use. Gapsor defects in the interface between the diffusing core and the plastictube placed over the core may also lead to “hot spots,” degradation ofdiffuser uniformity, and a decrease in power handling capability.

Accordingly, a light diffusing tip that overcomes the limitations ofconventional light diffusing tips would be advantageous.

BRIEF DESCRIPTION OF THE DRAWINGS

The purpose and advantages of the present disclosure will be apparent tothose of ordinary skill in the art from the following detaileddescription in conjunction with the appended drawings in which likereference characters are used to indicate like elements, and in which.

FIG. 1 is a schematic diagram illustrating an exemplary light applicatorin accordance with at least one embodiment of the present disclosure.

FIGS. 2-7 and 9 are cross-section views illustrating various exemplarylight diffusing tips in accordance with various embodiments of thepresent disclosure.

FIG. 8 is an isometric view illustrating an exemplary light diffusingtip having reflective material overlaying a portion of the tip inaccordance with at least one embodiment of the present disclosure,

FIGS. 10-13 are cross-section views illustrating an exemplary method ofmanufacturing a light diffusing tip in accordance with at least oneembodiment of the present disclosure.

FIG. 14 is a flow chart illustrating an exemplary method for utilizing alight applicator in accordance with at least one embodiment of thepresent disclosure.

DESCRIPTION OF THE DRAWINGS

FIGS. 1-14 illustrate various exemplary light diffusing applicators andexemplary methods of their use and manufacture. The devices and methodsdescribed herein may find advantageous application in the treatment ofsolid cancerous tumors and other defects in soft tissue. In at least oneembodiment of the disclosures made herein, a light diffusing applicatorincludes an optical waveguide designed for connection to an energysource and further includes an optical diffusing tip designed to causecylindrical or substantially cylindrical scattering of light radiationaround the axis of the optical waveguide.

The term light, as used herein, refers to electromagnetic radiationwithin any of the infrared, visible, and ultraviolet spectra.Consequently, the term light transmissive, as used herein, is used inthe context of the type of light implemented Exemplary sources of lightmay include, but are not limited to, lasers, light emitting diodes, arclamps, light bulbs, flash lamps, and the like.

Referring now to FIG. 1, an exemplary light applicator 10 is illustratedin accordance with at least one embodiment of the present disclosure Thelight applicator 10 includes a connector 11 coupled to a proximal end ofa flexible optical waveguide 12 and a light diffusing tip 13 opticallyand mechanically coupled to a distal end of the optical waveguide 12.The connector 11 couples to a light source (not shown) to receive lightenergy for transmission to the diffusing tip 13 via the waveguide 12. Anexample of the connector 11 includes the SMA905 fiber connector(available from Amphenol-Fiber Optic Products of Lisle, Ill.) which isfrequently used for stable and reliable coupling to common lasers andother light sources. The diffusing tip 13, in turn, scatters the lightenergy over a substantial portion of the diffusing tip 13. As disclosedin greater detail herein, in at least one embodiment, the diffusing tip13 comprises a light transmissive housing having a monolithic scatteringmedium disposed within the housing, where the monolithic scatteringmedium includes two or more distinct scattering regions, each scatteringregion comprising a scattering material having scattering propertiesdifferent from the scattering properties of the remaining scatteringregions. Additionally, each scattering region may be coextensive along alength of the tubing with one or more adjacent scattering regions sothat the diffusing tip exhibits a gradient in its scattering coefficientboth axially and radially.

Referring now to FIG. 2, an exemplary implementation of a lightdiffusing tip is illustrated in accordance with at least one embodimentof the present disclosure The illustrated diffusing tip 23 includes anoptical waveguide 22 having one or, more optical fiber cores 24surrounded by a cladding layer 25 and protective jacketing 26. A portionof the distal end of the optical waveguide 22 may be stripped of itsouter protective jacketing 26, thereby exposing the cladding 25 over alength of the fiber. In the illustrated example, the distal end of theoptical waveguide 22 is cleaved or polished flat, but other terminationconfigurations, such as termination in a point, ball or at an angle, maybe implemented as appropriate. The diffusing tip 23 further includes anouter housing 28 to enclose scattering material and to provide a surfacefor bonding the diffusing tip 23 to the optical waveguide 22. The outerhousing 28 preferably is composed of any of a variety of lighttransmissive materials, such as, for example, flexible PTFE or “Teflon,”polycarbonate, polyurethane, polyethylene, polypropylene, silicon,nylon, PVC, PET, ABS, PES, PEEK, FEP, as well as other flexible orrigid, radio-opaque or non radio-opaque materials as appropriate.

Disposed within the housing 28 is scattering material forming amonolithic scattering medium having two or more regions, where eachregion comprises a scattering material having one or more scatteringproperties that are distinct from the scattering properties of thescattering materials of the other regions In the illustrated example ofFIG. 2, the monolithic scattering medium disposed within the housing 28includes two scattering regions 30 and 31 The scattering region 30includes a scattering material 32 having one or more scatteringproperties that are distinct from the scattering material 33 comprisingthe scattering region 3 1. In at least one embodiment, the scatteringmaterial 32 of the scattering region 30 comprises scattering particles34 suspended in a light transmissive material 35 and the scatteringmaterial 33 comprises scattering particles 36 suspended in a lighttransmissive material 37. Examples of materials suitable for thescattering particles 34 and 36 include, but are not limited to plastics,glasses, metals, metal oxides, or other particles known in the art toscatter optical radiation. An exemplary commercial product which may beimplemented as scattering particles 34 or 36 includes titanium dioxideparticles available from Sigma-Aldrich Co. of St. Louis, Mo. Examples ofmaterials suitable for the light transmissive materials 35 and 37include, but are not limited to, plastics (such as described above withreference to the housing 28), epoxies, and elastomers such as siliconeor cyanoacrylates. An exemplary commercial product which may beimplemented as materials 35 or 37 includes Mastersil 151 two-partsilicone epoxy available from Master Bond, Inc., of Hackensack, N.J. Asdepicted by FIG. 2, the scattering material 32 (or, alternatively, thescattering material 33) further may be used as an adhesive to bond thehousing 28 to the fiber core 24 and/or cladding 26.

As noted above, the scattering material 32 and the scattering material33, in one embodiment, have one or more different scattering properties.Different scattering properties between the scattering materials 32 and33 may be implemented by, for example, utilizing one type of scatteringparticle 34 (e.g., titanium dioxide) for scattering material 32 and adifferent type of scattering particle 36 (e.g., gold particles) forscattering material 33. As another example, the scattering particles 34and 36 may be of different sizes and/or shapes so as to exhibitdifferent scattering properties. As a further example, the concentrationof the scattering particles 34 in the material 32 may be different thanthe concentration of scattering particles 36 in the material 37 so thatthe scattering materials 32 and 33 exhibit different scatteringproperties. It also should be noted that other configurations like gasbubbles in the elastomer or an emulsified liquid also may createscattering centers. Different scattering properties also may be achievedusing light transmissive materials with different indexes of refraction.The scattering materials 32 and 33 also may be different from each otherby a combination of any of scattering particle type, scattering particlesize, scattering particle shape, scattering particle concentration or atransmissive material's index of refraction. Typically, the differencebetween the scattering properties of the two materials 32 and 33 isrepresented by a difference in their scattering coefficients (i.e., ameasure of the amount of light scattering exhibited by a material).

In at least one embodiment, the scattering materials 32 and 33 arepositioned within the housing 28 such that the scattering regions 30 and31 are coextensive for, at least a portion 40 of the length of thehousing 28. In the example illustrated in FIG. 2, the scattering regions30 and 31 are arranged such that the scattering region 31 forms asubstantially cone shaped portion that is at least partially surroundedby material of the scattering region 30, and thus the scattering regions30 and 31 are coextensive along the housing 28 for part or all of thecone shaped region. As discussed in greater detail herein, thescattering regions 30 and 31 may be formed so as to take on any of avariety of shapes in the coextensive portion 40 of the housing 28 asappropriate.

As illustrated by cross-sections 42-44 at positions 45-47, respectively,of diffusing tip 23, the geometric relationship between the twoscattering regions 30 and 31 varies. As the distance from thetermination of the fiber core 24 increases, the cross-sectional area ofthe scattering material 32 decreases while the cross-sectional area ofthe scattering material 33 increases At point 45, the scattering mediumof the diffusing tip is made up of the scattering material 32,. At point46, the amount of scattering material 32 present decreases and theamount of scattering material 33 increases. At point 47, the scatteringelement of the diffusing tip 23 is almost entirely made up of thescattering material 33. Thus, the proportion of the scattering material33 to the scattering material 32 (i.e, the proportion of the scatteringregion 31 to the scattering region 30) of the monolithic scatteringmedium generally increases from the proximal end to the distal end ofthe diffusing tip 23. The distal end of diffusing tip 23 may be made upentirely of scattering material 33.

The concentration and length of both the scattering region 30 and thescattering region 31 within the diffusing tip 23 may be varied toachieve a desirable light distribution. For example, longer diffusingtips may have lower concentration scattering regions or shorter lengthsof higher concentration scattering regions. Similarly, shorter diffusingtips may contain a shorter length of a low concentration scatteringregion and a longer length of a higher concentration scattering region.

The concentration and length of each scattering region preferably isselected to result in substantially uniform emission of light along thelength of the diffusing tip. The intensity of light in a partiallytransmissive (i.e., scattering and/or absorptive) medium typicallyexhibits a fall-off described by Beer's Law, I=I_(o)e^(−μz), where Irepresents intensity at z, Io represents initial intensity, μ representsattenuation coefficient and z represents distance away from the source.Accordingly, the characteristics of the scattering regions may be chosenso as to make the light scattered along the length of the diffusing tipapproximately constant in view of Beer's Law. To illustrate, scatteringregions may be arranged so that the effective scattering coefficientμ(z)=−log(1−z/L)/z, for zε[0,L]. This may be achieved by, for example,arranging the scattering regions such that the overlapping segments haveprofiles substantially related by the preceding equation. As anotherexample, the scattering material 32 may have a lower concentration ofscattering particles 34 than the concentration of scattering particles36 of the scattering material 33 and, therefore, the effectiveconcentration of scattering particles increases over the coextensiveportion 40 even as the intensity of the light energy decreases. However,in certain instances it may be desirable to preferentially emit lightover a given cross section of the diffusing tip 23 which may beaccomplished by concentrating scattering material having higherscattering coefficients at positions where more light is intended toexit the diffusing tip 23.

Referring now to FIGS. 3 and 4, alternate exemplary implementations of alight diffusing tip are illustrated in accordance with at least oneembodiment of the present disclosure. FIG. 3 illustrates a diffusing tip71 comprising a monolithic scattering medium disposed within the housing28 and having two scattering regions 50 and 51. In contrast with thediffusing tip 23 of FIG. 2, the scattering region 50 includes ascattering material 52 having a substantially conical portion directedaway from the termination of the fiber core 24 and the scattering region51 includes a scattering material 53 having a region that at leastpartially surrounds the conical region and is therefore coextensive withthe scattering material 52 over the portion 48 of the length of thediffusing tip 71 In the illustrated embodiment, the scattering material52 has a lower scattering coefficient than the scattering material 53.As the cross-sections 54-56 at positions 57-59, respectively,illustrate, the proportion of the scattering material 52 to thescattering material 53 decreases, and the effective scatteringcoefficient therefore increases, as the distance from the termination ofthe fiber core 24 increases.

FIG. 4 illustrates another exemplary implementation of a diffusing tiphaving a monolithic scattering medium with two or more partiallyoverlapping, distinct scattering regions. FIG. 4 illustrates anexemplary diffusing tip having distinct scattering regions 60 and 61,wherein the scattering region 61 comprises a substantially conicalregion surrounded by the scattering region 60 over portion 49. Thescattering region 60 comprises a scattering material 62 having a firstscattering property and the scattering region 61 comprises scatteringmaterial 63 having a second scattering property different from the firstscattering property. Whereas the exemplary diffusing tips 23 and 71 ofFIGS. 2 and 3 are illustrated as having scattering regions that includeconical portions substantially coaxial with the axis of the housing 10,the axis of the substantially conical portion of scattering region 60 isoffset from the longitudinal axis of the housing 28, as illustrated bycross-sections 64-66 at positions 67-69, respectively. Such animplementation may be employed to preferentially scatter light out of agiven angular region of the diffusing tip. During the manufacture thediffusing tip, the scattering region 61 can be formed by allowing thescattering materials 62 and 63 to cure in the horizontal position or ina centrifuge, where the conical region 61 may settle due to gravity orcentrifugal force.

Referring now to FIGS. 5-7, exemplary diffusing tips having various capssecured to their distal ends are illustrated in accordance with at leastone embodiment of the present disclosure. FIG. 5 depicts a diffusing tip73 having a pointed cap 74 that facilitates insertion of the fiber intotissues for interstitial applications. FIG. 6 depicts a diffusing tip 83having a rounded cap 84 that may be used in hollow organs or to minimizerisk of vessel punctures during interstitial applications FIG. 7 depictsa diffusing tip 93 having a blunt cap 94 that represents a thirdscattering region having a scattering material with a high scatteringcoefficient for further minimizing forward propagation of light from thedistal end of the diffusing tip 93. Blunt cap 94 may also be made of abiocompatible material to prevent contact of scattering material withbodily tissue.

Referring now to FIGS. 8 and 9, exemplary treatments to the housing ofthe diffusing tip are illustrated in accordance to at least oneembodiment of the present disclosure. FIG. 8 depicts an exemplarydiffusing tip 103 with a selective angular emission profile that isachieved using a reflective material 104 overlaying a section of thesurface of the housing 28 of the diffusing tip 103, where the reflectivematerial 104 prevents light energy from passing through that section.Suitable materials for the reflective material 104 include, for example,deposited surfaces of gold, silver, aluminum, chrome, nickel, or otherreflective materials. The reflective material 104 may be disposed eitheron the inner surface or outer surface of the housing 28. FIG. 9 depictsan exemplary diffusing tip 113 having a non-stick coating 114 disposedon some or all of the outer surface of the housing 28. The non-stickcoating 114 may include, for example, any of a number of lighttransmissive fluoropolymers with high temperature handling capabilityand non-stick surface properties with respect to thermally coagulatedtissues Materials for the housing 28 can then be chosen based on thedesired stiffness of the diffusing tip while the non-stick coating 114of fluoropolymer provides the ideal surface properties. Alternatively,the non-stick coating 114 may be used to provide increased stiffness ordurability for the diffusing tip 113.

Referring now to FIGS. 10-13, an exemplary method for manufacturing alight diffusing tip is illustrated in accordance with at least oneembodiment of the present disclosure Initially, a scattering materialhaving a lower scattering coefficient is created, for example, by mixinga lower amount of scattering particles in an elastomer material tocreate a scattering material with a lower concentration of scatteringparticles. A scattering material having a higher scattering coefficientalso is created. The scattering material having a higher scatteringcoefficient may be created by, for example, mixing a higher amount ofscattering particles in an elastomer material to create a scatteringmaterial having a higher concentration of scattering particles. Toillustrate, the scattering particle and elastomer mixtures may include,for example, titanium dioxide particles mixed in silicone epoxy. Inorder to minimize or eliminate air bubbles in the scattering materials,a vacuum may be applied to the uncured silicone/titanium dioxide mixtureprior to use.

In certain instances, the scattering particle concentration range forthe lower scattering coefficient material and the higher scatteringcoefficient material varies depending on the length and core diameter ofthe optical waveguide. For a typical 400 micron core diameter opticalwaveguide, a diffusing tip of for example, 10 mm in length typically hasa lower scattering coefficient material with a concentration of TiO₂scattering particles preferably between 100 mg/ml and 180 mg/ml and morepreferably between 145 mg/ml and 155 mg/ml. The higher scatteringcoefficient material typically has a concentration of TiO₂ scatteringparticles preferably between 2500 mg/ml and 6500 mg/ml and morepreferably between 4400 mg/ml and 4650 mg/ml. The scattering regionsformed from the scattering materials also may vary in length Toillustrate, for the same 10 mm long diffusing tip, the length of thescattering region resulting from the lower scattering coefficientmaterial preferably is between 1 mm and 100 mm, more preferably between5 mm and 10 mm and even more preferably is about 6 mm. For the samediffusing tip length, the length of the scattering region formed fromthe higher scattering coefficient material preferably is between 1 mmand 100 mm, more preferably is between 2 mm and 5 mm and even morepreferably is about 4 mm. The shapes and lengths of each scatteringregion and the concentration of each scattering material may be variedto achieve the desired output profile for light emitted from thediffusing tip,

Referring to FIG. 10, lower scattering coefficient material 122 istransferred to a first injector barrel 124 (e.g., a 3 cc barrelavailable from EFD, Inc. of East Providence, R.I.) supplied with a bluntended needle 125 (e.g., a 27 Ga needle available from EFD, Inc.). Ahousing 126 is positioned over the distal end of an optical waveguide128 over a length where the protective jacket has previously beenremoved from the optical waveguide 128. In at least one embodiment, thehousing 126 includes a tubular housing having an outer diameter selectedto substantially match the outer diameter of the optical waveguide'sprotective jacket so that a uniform surface profile is provided alongthe entire length of the resulting light applicator The wall thicknessof the housing 126 may be selected to allow space for a bonding region130 between the inner wall of the housing 126 and the exposed claddingon the optical waveguide 128.

Referring to FIG. 11, the needle 125 is introduced into the distal endof the housing 126 and a plunger tip 131 within barrel 124 is actuatedeither manually or using a regulated dispenser (for example, the EFDUltra Dispenser available from EFD, Inc.) to inject lower scatteringcoefficient material 122 into the lumen of the housing 126. The lowerscattering coefficient material 122 may be injected until, for example,the distance 132 between the end of the optical waveguide 128 and theblunt ended needle 125 and approximately half the length 129 of housing126 covering the exposed end of the optical waveguide 128 are filled. Atthis point, the needle 125 may be removed from the distal end of thehousing 126 while continuing to inject.

Referring to FIG. 12, the higher scattering coefficient material 134 istransferred to a second injector barrel 136 supplied with a second bluntended needle 137. The needle 137 then is positioned inside the distalend of the housing 126. Actuation of plunger tip 138 infuses higherscattering coefficient material 134 into a portion of the lowerscattering coefficient material 122 which results in the formation of adiscrete substantially cone-shaped portions of higher scatteringcoefficient material 134 within the lower scattering coefficientmaterial 122 over a length 140 of the housing 126. During injection ofhigher scattering coefficient material 134, lower scattering coefficientmaterial 122 is forced toward the optical waveguide 128 and allowed tofill the bonding region 130 between the housing 126 and the exposedcladding of the optical waveguide 128. At this point the needle 137 isremoved from the housing 126 while continuing to inject. Alternatively,the higher scattering coefficient material 134 may be inserted via theproximal end of the housing 126 and the optical waveguide 128subsequently inserted before or during the curing of the scatteringmaterial 134.

As illustrated by FIG. 13, the distal end of the resulting diffusing tip143 may be cut or otherwise trimmed to the appropriate length, and thefinished tip/fiber assembly may be positioned vertically and thescattering materials 132 and 134 allowed to cure. Alternatively, thediffusing tip 143 may be placed in a horizontal position or subjected toa centrifuge so as to cause the scattering particles of the scatteringmaterials 132 and 134 to settle in one or more desired locations Thus,as FIGS. 10-13 illustrate, although injected as two separatepreparations, the scattering materials 132 and 134 may be formulated ofthe same base material and thus cure into a monolithic scattering mediumwith spatially varying (both longitudinally and radially) scatteringparticle concentrations.

Although FIGS. 11-13 illustrate an exemplary method for manufacturing adiffusing tip, other techniques may be implemented without departingfrom the spirit or the scope of the present invention. For example, thediffusing tip may be formed by inserting one type of scattering materialinto the housing 126 and allowing the scattering material to partiallyor fully cure. A cavity is then formed in one end of the scatteringmaterial using, for example, a drill bit or scraping tool.Alternatively, a mold having the desired cavity shape may be insertedinto one end of the scattering material prior to curing and then removedafter the first scattering material has at least partially cured.Another type of scattering material then is inserted into the housing126 so that it occupies the cavity in formed the first scatteringmaterial. The second scattering material then may be left to cure andbond to the first scattering material so as to form the scatteringmedium of the resulting diffusing tip.

While several specific geometric shapes and relationships for thediscrete scattering regions have been disclosed herein, any suitablearrangement of scattering regions may be implemented using the teachingsprovided herein without departing from the spirit or scope of thepresent disclosure. For example, the shape of the a scattering region isgenerally described herein as being conical in shape and increasinglinearly in size from proximal to distal ends, but alternatively itsshape could have a non-linear taper, such as in accordance with Beer'sLaw, or other geometric shape and still achieve a desired effect. Assuch, there are many suitable modifications and variations in theshapes, sizes, lengths, and positional arrangements of the discretescattering regions that are within the scope of the present disclosure

Referring now to FIG. 14, an exemplary method 140 of use of a lightapplicator having a diffusing tip is illustrated in accordance with atleast one embodiment. Generally, the exemplary method 140 initiates atstep 142 wherein a light applicator having a diffusing tip (e.g., thelight applicator 10 of FIG. 1) is obtained. The light applicator thenmay be affixed or otherwise coupled to a light source via the connector11 (FIG. 1). At step 144, the diffusing tip is placed on or in a patientand the light diffusing tip is located proximate to the bodily tissue tobe treated. At step 146, the light source is activated and light energyis transmitted to the diffusing tip 13 (FIG. 1) via the connector 11 andthe optical waveguide 12 (FIG. 1). Upon reaching the diffusing tip 13,the light is scattered along and out of the monolithic scattering mediumin accordance with the scattering properties of the two or more distinctscattering regions of the monolithic scattering medium so as toirradiate the bodily tissue proximal to the diffusing tip 13. As notedabove, in one embodiment, the two or more scattering regions haveparticular scattering properties and overlap in such a way so as toprovide a substantially uniform light scattering along the length of thediffusing tip. In other embodiments, the scattering regions may bearranged so as to concentrate the light scattering in certain areas orin certain directions. Specific implementations of the general method140 may include, for example LITT treatment of focal or metastatictumors in brain, prostate, kidney, liver, breast, uterine, spinal, boneor other organs, as well as photodynamic therapy in hollow organs.

The previous description is intended to convey a thorough understandingof the present disclosure by providing a number of specific embodimentsand details involving light diffusion techniques. It is understood,however, that the present disclosure is not limited to these specificembodiments and details, which are exemplary only. It is furtherunderstood that one possessing ordinary skill in the art, in light ofknown systems and methods, would appreciate the use of the disclosurefor its intended purposes and benefits in any number of alternativeembodiments, depending upon specific design and other needs.

1. A method comprising: providing a housing; forming a monolithic lightscattering medium within the housing, the monolithic light scatteringmedium including a first scattering region having a first scatteringproperty and a second scattering region having a second scatteringproperty different from the first scattering property, wherein the firstscattering region and the second scattering region are coextensive alonga substantial portion of a length of the housing.
 2. The method of claim1, wherein forming the monolithic light scattering medium comprises:inserting a first scattering material into a first end of the housing toform the first scattering region, the first scattering material havingthe first scattering property; and inserting a second scatteringmaterial into the housing so as to contact a portion of the firstscattering region over a substantial portion of the length of thehousing to form the second scattering region, the second scatteringmaterial having the second scattering property; and curing the firstscattering material and the second scattering material to form amonolithic scattering medium.
 3. The method of claim 2, whereininserting the second scattering material includes inserting the secondscattering material to displace at least a portion of the firstscattering material.
 4. The method of claim 3, wherein inserting thesecond scattering material includes inserting the second material toform a conical shape.
 5. The method of claim 2, wherein the firstscattering material includes a first concentration of scatteringparticles suspended in a light transmissive material and the secondscattering material includes a second concentration of the scatteringparticles suspended in a light transmissive material.
 6. The method ofclaim 2, wherein the first scattering material includes a first type ofscattering particle suspended in a light transmissive material and thesecond scattering material includes a second type of scattering particlesuspended in a light transmissive material.
 7. The method of claim 2,further comprising: inserting a portion of at least one opticalwaveguide into one of the first or second scattering materials prior tocuring.
 8. A method of forming an applicator, the method comprising:inserting a first scattering material into a first end of a housing toform a first scattering region, the first scattering material having afirst scattering property; and inserting a second scattering materialinto the housing so as to contact a portion of the first scatteringregion over a substantial portion of the length of the housing to form asecond scattering region, the second scattering material having thesecond scattering property; and curing the first scattering material andthe second scattering material to form a monolithic scattering medium.9. The method of claim 8, further comprising mixing a scatteringmaterial at a concentration of 100 mg/ml to 180 mg/ml with a polymer toform the first scattering material.
 10. The method of claim 8, furthercomprising mixing a scattering material at a concentration of 2500 mg/mlto 6500 mg/ml with a polymer to form the second scattering material. 11.The method of claim 8, further comprising applying a vacuum to the firstscattering material and to the second scattering material prior tocuring the first scattering material and the second scattering material.12. The method of claim 8, wherein inserting the second scatteringmaterial includes inserting the second scattering material to displaceat least a portion of the first scattering material.
 13. The method ofclaim 12, wherein inserting the second scattering material includesinserting the second material to form a conical shape.
 14. The method ofclaim 13, wherein the conical shape is coaxial with the housing.
 15. Themethod of claim 13, wherein the conical shape is offset from thelongitudinal axis of the housing.
 16. The method of claim 8, wherein thesecond scattering material is inserted into the first end of thehousing.
 17. The method of claim 8, further comprising positioning thehousing horizontally while curing the first and second scatteringmaterials.
 18. The method of claim 8, wherein the housing is subjectedto a centrifuge while curing the first and second scattering materials.19. The method of claim 8, further comprising: inserting a portion of atleast one optical waveguide into one of the first or second scatteringmaterials prior to curing.
 20. A method comprising: providing a lightapplicator having a light diffusing tip coupled to a first end of anoptical waveguide of the light applicator, the light diffusing tipcomprising a housing and a monolithic light scattering medium disposedwithin the housing, the light scattering medium including a firstscattering region having a first scattering property and a secondscattering region having a second scattering property different from thefirst scattering property, wherein the first scattering region and thesecond scattering region are coextensive along a substantial portion ofa length of the housing; locating the light diffusing tip proximal to abodily tissue; and providing light energy to the light diffusing tip viaa second end of optical waveguide of the light applicator so as toirradiate the bodily tissue.
 21. The method of claim 20, wherein thebodily tissue is a tumor.
 22. The method of claim 20, wherein the bodilytissue is irradiated as part of photodynamic therapy.